- This variant has been named as the Delta variant by the WHO.
- The Delta variant was first detected in India in December 2020 and became the most commonly reported variant in the country from mid-April 2021.
- The variant could be more than twice as transmissible as the original strain of SARS-CoV-2.
- The variant was first detectable in infected people four days after exposure, compared with an average of six days among infected people with the original virus, suggesting enhanced replication of this variant.
- Individuals infected with this variant also had viral loads up to 1,260 times higher than those in people infected with the original virus.
- The Delta variant is now contributing to a surge of cases around the world. It now makes up more than 80% of new cases in the United States
- As of July 2021, the variant had been detected in more than 130 countries.
- In the UK, there has been a rapid increase in cases with this variant associated with travel to India and community transmission. The Delta variant already makes up more than 90% of all infections.
- Growth rates show that the Delta variant is growing faster than the Alpha variant.
- A modeling study predicts that there is a “realistic possibility” that B.1.617.2 is 60% more transmissible than the Alpha variant (B.1.1.7).
- Variant is defined by 19R, (G142D), 156del, 157del, R158G, L452R, T478K, D614G, P681R, D950N mutations in the spike protein.
- Several of these mutations may impact on immune responses directed towards the key antigenic regions of receptor binding protein (452 and 478) and deletion of part of the N terminal domain (156 and 157).
- P681R mutation changes an amino acid at a spot directly beside the furin cleavage site, a key step enabling the virus to invade human cells, thus enhancing viral infectivity.
Viral infection and transmission in a large, well-traced outbreak caused by the SARS-CoV-2 Delta variant
Medrxiv, July 23, 2021
Rapid displacement of SARS-CoV-2 variant B.1.1.7 by B.1.617.2 and P.1 in the United States
Medrxiv, June 21, 2021